[AArch64] Use LateSimplifyCFG after expanding atomic operations.

Summary:
After r308422 we defer optimizations that can destroy loop canonical forms to
LateSimplifyCFG. Running LateSimplifyCFG after expanding atomic operations
can exploit more control-flow opportunities.

Reviewers: mcrosier, t.p.northover, efriedma

Reviewed By: efriedma

Subscribers: aemerson, rengolin, javed.absar, llvm-commits, kristof.beyls

Differential Revision: https://reviews.llvm.org/D38262

llvm-svn: 314857

3 files changed, 64 insertions, 4 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp b/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp
index e65b382e85b..1762475ac93 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp
+++ b/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp
@@ -365,7 +365,7 @@ void AArch64PassConfig::addIRPasses() {
   // determine whether it succeeded. We can exploit existing control-flow in
   // ldrex/strex loops to simplify this, but it needs tidying up.
   if (TM->getOptLevel() != CodeGenOpt::None && EnableAtomicTidy)
-    addPass(createCFGSimplificationPass());
+    addPass(createLateCFGSimplificationPass());
 
   // Run LoopDataPrefetch
   //
diff --git a/llvm/test/CodeGen/AArch64/aarch64-loop-gep-opt.ll b/llvm/test/CodeGen/AArch64/aarch64-loop-gep-opt.ll
index 2b4e438a13a..1b2ed4b8952 100644
--- a/llvm/test/CodeGen/AArch64/aarch64-loop-gep-opt.ll
+++ b/llvm/test/CodeGen/AArch64/aarch64-loop-gep-opt.ll
@@ -19,9 +19,9 @@ entry:
 
 do.body.i:
 ; CHECK-LABEL: do.body.i:
-; CHECK:          %uglygep1 = getelementptr i8, i8* %uglygep, i64 %3
-; CHECK-NEXT:     %4 = bitcast i8* %uglygep1 to i32*
-; CHECK-NOT:      %uglygep1 = getelementptr i8, i8* %uglygep, i64 1032
+; CHECK:          %uglygep2 = getelementptr i8, i8* %uglygep, i64 %3
+; CHECK-NEXT:     %4 = bitcast i8* %uglygep2 to i32*
+; CHECK-NOT:      %uglygep2 = getelementptr i8, i8* %uglygep, i64 1032
 
 
   %0 = phi i32 [ 256, %entry ], [ %.be, %do.body.i.backedge ]
diff --git a/llvm/test/CodeGen/AArch64/cmpxchg-idioms.ll b/llvm/test/CodeGen/AArch64/cmpxchg-idioms.ll
index 0c008c26979..cae09b28979 100644
--- a/llvm/test/CodeGen/AArch64/cmpxchg-idioms.ll
+++ b/llvm/test/CodeGen/AArch64/cmpxchg-idioms.ll
@@ -91,3 +91,63 @@ end:
 
 declare void @bar()
 declare void @baz()
+
+define i1 @test_conditional2(i32 %a, i32 %b, i32* %c) {
+; CHECK-LABEL: test_conditional2:
+; CHECK: [[LOOP:LBB[0-9]+_[0-9]+]]:
+; CHECK: ldaxr [[LOADED:w[0-9]+]], [x19]
+; CHECK: cmp [[LOADED]], w21
+; CHECK: b.ne [[FAILED:LBB[0-9]+_[0-9]+]]
+
+; CHECK: stlxr [[STATUS:w[0-9]+]], w20, [x19]
+; CHECK: cbnz [[STATUS]], [[LOOP]]
+; CHECK: orr [[STATUS]], wzr, #0x1
+; CHECK: b [[PH:LBB[0-9]+_[0-9]+]]
+
+; CHECK: [[FAILED]]:
+; CHECK-NOT: cmp {{w[0-9]+}}, {{w[0-9]+}}
+
+; verify the preheader is simplified by latesimplifycfg.
+; CHECK: [[PH]]:
+; CHECK: orr w22, wzr, #0x2
+; CHECK-NOT: orr w22, wzr, #0x4
+; CHECK-NOT: cmn w22, #4
+; CHECK: b [[LOOP2:LBB[0-9]+_[0-9]+]]
+; CHECK-NOT: b.ne [[LOOP2]]
+; CHECK-NOT: b {{LBB[0-9]+_[0-9]+}}
+; CHECK: bl _foo
+entry:
+  %pair = cmpxchg i32* %c, i32 %a, i32 %b seq_cst seq_cst
+  %success = extractvalue { i32, i1 } %pair, 1
+  br label %for.cond
+
+for.cond:                                         ; preds = %if.end, %entry
+  %i.0 = phi i32 [ 2, %entry ], [ %dec, %if.end ]
+  %changed.0.off0 = phi i1 [ %success, %entry ], [ %changed.1.off0, %if.end ]
+  %dec = add nsw i32 %i.0, -1
+  %tobool = icmp eq i32 %i.0, 0
+  br i1 %tobool, label %for.cond.cleanup, label %for.body
+
+for.cond.cleanup:                                 ; preds = %for.cond
+  %changed.0.off0.lcssa = phi i1 [ %changed.0.off0, %for.cond ]
+  ret i1 %changed.0.off0.lcssa
+
+for.body:                                         ; preds = %for.cond
+  %or = or i32 %a, %b
+  %idxprom = sext i32 %dec to i64
+  %arrayidx = getelementptr inbounds i32, i32* %c, i64 %idxprom
+  %0 = load i32, i32* %arrayidx, align 4
+  %cmp = icmp eq i32 %or, %0
+  br i1 %cmp, label %if.end, label %if.then
+
+if.then:                                          ; preds = %for.body
+  store i32 %or, i32* %arrayidx, align 4
+  tail call void @foo()
+  br label %if.end
+
+if.end:                                           ; preds = %for.body, %if.then
+  %changed.1.off0 = phi i1 [ false, %if.then ], [ %changed.0.off0, %for.body ]
+  br label %for.cond
+}
+
+declare void @foo()